HTTP is fast, HTTPS really slow and causes massive FCS failure

Be careful with the captures taken from you VE, it automatically adds some trailing information/ debugging details, you need to install a plugin in your wireshark to have access to it (you can easily find it devcentral). If you don't have the plugin is normal you see the FCS errors.

Regarding the slowness, it looks like the problem is mainly in the images. Can you configure an http acceleration profile to cache the images in your VE and see the difference? Maybe your problem is on the backend server. I suggest you try first HTTP1.1 and when you solve the problem you continue with HTP2.